1. Field of the Invention
The present invention relates to an ultrasonic probe including plural ultrasonic transducers for transmitting and receiving ultrasonic waves, and an ultrasonic diagnostic apparatus for generating ultrasonic diagnostic images by using the ultrasonic probe.
2. Description of a Related Art
In medical fields, various imaging technologies have been developed for observation and diagnoses within an object to be inspected. Especially, ultrasonic imaging for acquiring interior information of the object by transmitting and receiving ultrasonic waves enables image observation in real time and provides no exposure to radiation unlike other medical image technologies such as X-ray photography or RI (radio isotope) scintillation camera. Accordingly, ultrasonic imaging is utilized as an imaging technology at a high level of safety in a wide range of departments including not only the fetal diagnosis in obstetrics, but also gynecology, circulatory system, digestive system, and so on.
The principle of ultrasonic imaging is as follows. Ultrasonic waves are reflected at a boundary between regions having different acoustic impedances like a boundary between structures within the object. Therefore, by transmitting ultrasonic beams into the object such as a human body, receiving ultrasonic echoes generated within the object, and obtaining reflection points where the ultrasonic echoes are generated or reflection intensity, outlines of structures (e.g., internal organs, diseased tissues, and so on) existing within the object can be extracted.
Generally, in an ultrasonic diagnostic apparatus, an ultrasonic probe including plural ultrasonic transducers (vibrators) having transmitting and receiving functions of ultrasonic waves is used. Reception signals outputted from the vibrators, which have received ultrasonic echoes, have delays according to differences of distances from the focal point of ultrasonic waves to the respective vibrators. Accordingly, beam forming processing (reception focusing processing) for forming a focal point in a specific position is performed by providing the delays according to the positions of the vibrators to those reception signals and then adding those reception signals to one another. In this regard, until the reception signals are added to one another, those reception signals are handled as parallel data.
The reception focusing processing is typically performed by digital signal processing. That is, the A/D-converted reception signals are accumulated in a memory, and then, read out while the readout times are changed as needed, moderately interpolation-processed, and added to one another. When the reception signals are added to one another, the number of signal channels becomes one, and therefore, signal transmission can be performed by wireless communication. Accordingly, if a circuit for performing reception focusing processing is incorporated in the ultrasonic probe, a number of signal lines connecting the ultrasonic probe with the ultrasonic diagnostic apparatus main body can be reduced, or wireless communication can be realized.
However, in the reception focusing processing, the amounts of delay provided to the reception signals are different depending on the position of the focal point, and therefore, the control of the readout times from the memory becomes extremely complex, and a large-scale circuit is necessary. If such a circuit is incorporated into the ultrasonic probe, the probe becomes too large in size for practical use to be easily operated with one hand.
As a related technology, Japanese Patent Application Publication JP-P2003-299648A discloses an ultrasonic diagnostic apparatus having an ultrasonic probe that can maintain and improve operability because a thinner and lighter transmission cable can be realized even when a number of vibrating elements is increased with higher definition. The ultrasonic diagnostic apparatus includes an ultrasonic probe for transmitting and receiving ultrasonic pulses to and from a living body by using plural vibrating elements, and an apparatus main body connected to the ultrasonic probe via a transmission cable, for generating transmission signals for transmitting ultrasonic pulses from the ultrasonic probe and forming an ultrasonic image from reception signals based on ultrasonic pulses (echoes) reflected by the living body and received by the ultrasonic probe. The ultrasonic diagnostic apparatus is characterized in that the transmission signals and the reception signals passed between the ultrasonic probe and the apparatus main body via the transmission cable are time-divisionally segmented corresponding to the respective vibrating elements and chipped before transmission and the respective chips are sequentially transmitted by using a common signal line within the transmission cable.
However, in the ultrasonic diagnostic apparatus of JP-P2003-299648A, since the reception signals outputted from the respective vibrating elements are transmitted in an unchanged band, the volume of data cannot be reduced and a high transmission rate is necessary. Further, since the reception signals are time-divisionally transmitted, there is no guarantee that the beam forming processing can reliably be performed after transmission.
Further, Japanese Patent Application Publication JP-P2008-18107A discloses a wireless ultrasonic diagnostic apparatus for wireless transmission between an ultrasonic probe and an apparatus main body. In the ultrasonic diagnostic apparatus, the ultrasonic probe includes plural vibrators, amplifiers and A/D (analog/digital) converters corresponding to those vibrators, a digital beamformer, a PS (parallel/serial) converting unit, a control data inserting unit, a modulator, and a power amplifier. The digital beam forming processing is performed within the ultrasonic probe to generate phase-matched and added data, and further, the phase-matched and added data is parallel/serial-converted.
However, in order to perform digital beam forming processing within the ultrasonic probe, a front-end circuit in a conventional ultrasonic diagnostic apparatus as a whole should be accommodated within the ultrasonic probe, and the circuit size becomes enormous.